Long term evolution radio access network

ABSTRACT

A system, a method, and a computer program product for coordinating communication of data packets between a user device and a core network are disclosed. The system includes a first device communicatively coupled to the core network, a second device communicatively coupled to the first device. The second device receives signals from the user device. The first device and the second device share at least one functionality associated with layer 2 of a long term evolution radio access network.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and is a Continuation of U.S.patent application Ser. No. 14/179,421, filed Feb. 12, 2014, entitled,“Long Term Evolution Radio Access Network,” which claims priority to andbenefit under 35 U.S.C. § 119(e) to U.S. Provisional Patent ApplicationNo. 61/763,927, filed Feb. 12, 2013, and entitled “Long Term Evolution(LTE) Radio Access Network (Ran) Architecture,” and incorporates theirdisclosures herein by reference in their entireties.

TECHNICAL FIELD

The subject matter described herein generally relates to data processingand in particular, to a long term evolution radio access network.

BACKGROUND

In today's world, cellular networks provide on-demand communicationscapabilities to individuals and business entities. Typically, a cellularnetwork is wireless network that can be distributed over land areas,which are called cells. Each such cell is served by at least onefixed-location transceiver, which is referred to as a cell site or abase station. Each cell can use a different set of frequencies than itsneighbor cells in order to avoid interference and provide guaranteedbandwidth within each cell. When cells are joined together, they provideradio coverage over a wide geographic area, which enables a large numberof mobile telephones, and/or other wireless devices or portabletransceivers to communicate with each other and with fixed transceiversand telephones anywhere in the network. Such communications areperformed through base stations and are accomplished even if when mobiletransceivers are moving through more than one cell during transmission.Major wireless communications providers have deployed such cell sitesthroughout the world, thereby allowing communications mobile phones andmobile computing devices to be connected to the public switchedtelephone network and public Internet.

A mobile telephone is a portable telephone that is capable of receivingand/or making telephone and/or data calls through a cell site or atransmitting tower by using radio waves to transfer signals to and fromthe mobile telephone. In view of a large number of mobile telephoneusers, current mobile telephone networks provide a limited and sharedresource. In that regard, cell sites and handsets can change frequencyand use low power transmitters to allow simultaneous usage of thenetworks by many callers with less interference. Coverage by a cell sitecan depend on a particular geographical location and/or a number ofusers that can potentially use the network. For example, in a city, acell site can have a range of up to approximately ½ mile; in ruralareas, the range can be as much as 5 miles; and in some areas, a usercan receive signals from a cell site 25 miles away.

The following are examples of some of the digital cellular technologiesthat are in use by the communications providers: Global System forMobile Communications (“GSM”), General Packet Radio Service (“GPRS”),cdmaOne, CDMA2000, Evolution-Data Optimized (“EV-DO”), Enhanced DataRates for GSM Evolution (“EDGE”), Universal Mobile TelecommunicationsSystem (“UMTS”), Digital Enhanced Cordless Telecommunications (“DECT”),Digital AMPS (“IS-136/TDMA”), and Integrated Digital Enhanced Network(“iDEN”). The Long Term Evolution, or 4G LTE, which was developed by theThird Generation Partnership Project (“3GPP”) standards body, is astandard for a wireless communication of high-speed data for mobilephones and data terminals. LTE is based on the GSM/EDGE and UMTS/HSPAdigital cellular technologies and allows for increasing capacity andspeed by using a different radio interface together with core networkimprovements.

Communications between users in existing digital cellular networks aretypically defined and/or affected by various factors and/or parameters.These can include latency. Latency can be measured as either one-way(the time from the source sending a packet to the destination receivingit), or a round-trip delay time (the one-way latency from source todestination plus the one-way latency from the destination back to thesource). While the existing LTE systems were designed to increase speedof communications by reducing significant latency that plagued itspredecessors, such systems are still affected by a substantial amount oflatency when mobile users setup communications via the LTE systems.Further, the current LTE systems involve components that are costly andexpensive to install and maintain. Thus, there is need to provide anefficient and a cost-effective solution to existing LTE system that arecapable of further reduction in latency.

SUMMARY

In some implementations, the current subject matter relates to a system(as well as a method and/or a computer program product) for coordinatingcommunication of data packets between a user device and a core network.The system can include a first device communicatively coupled to thecore network, and a second device communicatively coupled to the firstdevice and configured for receiving signals from the user device. Thefirst device and the second device can share at least one functionalityassociated with layer 2 of a long term evolution radio access network.

In some implementations, the current subject matter can also include oneor more of the following optional features. The first device can includeat least a portion of an evolved node (eNodeB) base station. The seconddevice can include a remote radio head. The remote radio head caninclude a radio transmitter and a radio receiver. In someimplementations, the functionality shared by the first and second devicecan be a packet data convergence protocol (“PDCP”).

In some implementations, the first device and the second device can becommunicatively coupled via a fronthaul Ethernet connection. The firstdevice can be communicatively coupled with the core network using abackhaul connection. At least one message in a plurality of messages cantraverse the fronthaul Ethernet connection. The messages can beassociated with establishing communication between the user device andthe core network. The plurality of messages can include messagesrelating to layer 1 and/or layer 2 configuration and messages relatingto establishing a radio resource control (“RRC”) connection. In someimplementations, the messages relating to layer 1 and/or layer 2configuration can be combined with messages relating to establishing theRRC connection, which can reduce latency associated with the Ethernetfronthaul connection. The messages can also include messages relating tore-establishing the RRC connection. Further, in some implementations,the messages relating to layer 1 and/or layer 2 configuration can becombined with the messages relating to re-establishing the remote radiocontrol RRC connection, which can also reduce latency associated withthe Ethernet fronthaul connection.

In some implementations, the system can include a third devicecommunicatively coupled to the core network. The third device caninclude at least one of the following: at least a portion of an evolvednode (eNodeB) base station and a remote radio head. The first device andthe third device can be at least one of the following: a macro cell anda micro cell. The first device and the third device can exchange aplurality of messages relating to handover. The messages exchangedbetween the first device and the third device can also include messagesrelating to layer 1 and/or layer 2 configuration. In someimplementations, the messages relating to handover can be combined withmessages relating to layer 1 and/or layer 2 configuration. In someimplementations, at least one of the second device and the third device,upon detecting a reconfiguration of a connection with the user device,can begin transmission of data on a downlink connection connecting theuser device and at least one of the second device and the third device.

In some implementations, the current subject matter can relate to asystem (as well as a method and/or a computer program product) forcoordinating communication of data packets between a user device and acore network. The system can include a communications device that can becommunicatively coupled to the core network via a backhaul connection.The communications device can have at least one functionality associatedwith layer 2 of a long term evolution radio access network. In someimplementations, the communications device can include at least aportion of an evolved node (eNodeB) base station, where thefunctionality can relate to packet data convergence protocol (PDCP).

In some implementations, the current subject matter can relate to asystem (as well as a method and/or a computer program product) forcoordinating communication of data packets between a user device and acore network. The system can include a first communications device thatcan receive at least one data packet from the user device. The firstcommunications device can have at least one functionality associatedwith layer 2 of a long term evolution radio access network. In someimplementations, the first communications device can include a remoteradio head. The remote radio head can include a radio transmitter and aradio receiver. The functionality can relate to packet data convergenceprotocol (PDCP). Further, in some implementations, the firstcommunications device can be communicatively coupled to a second deviceusing a fronthaul Ethernet connection for exchanging at least onemessage relating to layer 1 and/or layer 2 configuration and/orestablishing a radio resource control (RRC) connection using PDCP.

Articles are also described that comprise a tangibly embodiedmachine-readable medium embodying instructions that, when performed,cause one or more machines (e.g., computers, etc.) to result inoperations described herein. Similarly, computer systems are alsodescribed that can include a processor and a memory coupled to theprocessor. The memory can include one or more programs that cause theprocessor to perform one or more of the operations described herein.Additionally, computer systems may include additional specializedprocessing units that are able to apply a single instruction to multipledata points in parallel.

The details of one or more variations of the subject matter describedherein are set forth in the accompanying drawings and the descriptionbelow. Other features and advantages of the subject matter describedherein will be apparent from the description and drawings, and from theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, show certain aspects of the subject matterdisclosed herein and, together with the description, help explain someof the principles associated with the disclosed implementations. In thedrawings,

FIG. 1a illustrates an exemplary conventional long term evolution(“LTE”) communications system;

FIG. 1b illustrates further detail of the exemplary LTE system shown inFIG. 1 a;

FIG. 1c illustrates additional detail of the evolved packet core of theexemplary LTE system shown in FIG. 1 a;

FIG. 1d illustrates an exemplary evolved Node B of the exemplary LTEsystem shown in FIG. 1 a;

FIG. 2 illustrates further detail of an evolved Node B shown in FIGS. 1a-d;

FIG. 3 illustrates an exemplary intelligent Long Term Evolution RadioAccess Network, according to some implementations of the current subjectmatter;

FIG. 4a illustrates an exemplary intelligent Long Term Evolution RadioAccess Network implementing carrier aggregation feature, according tosome implementations of the current subject matter;

FIG. 4b-c illustrate exemplary dynamic point selection and coordinatedscheduling/beam-forming in the Long Term Evolution Radio Access Network;

FIGS. 5a-d illustrate exemplary inter-eNodeB handover procedures,according to some implementations of the current subject matter;

FIGS. 6a-c illustrate exemplary intra-eNodeB handover procedures,according to some implementations of the current subject matter;

FIGS. 7a-h illustrate exemplary RRC connection establishment procedures,according to some implementations of the current subject matter;

FIGS. 8a-d illustrate exemplary RRC connection re-establishmentprocedures, according to some implementations of the current subjectmatter; and

FIG. 9 illustrates an exemplary system, according to someimplementations of the current subject matter.

FIG. 10 illustrates an exemplary method, according to someimplementations of the current subject matter.

DETAILED DESCRIPTION

To address the deficiencies of currently available solutions, one ormore implementations of the current subject matter provide long termevolution radio access network having an intelligent capability.

I. Long Term Evolution Communications System

FIGS. 1a-c and 2 illustrate an exemplary conventional long termevolution (“LTE”) communication system 100 along with its variouscomponents. An LTE system or a 4G LTE, as it commercially known, isgoverned by a standard for wireless communication of high-speed data formobile telephones and data terminals. The standard is based on theGSM/EDGE (“Global System for Mobile Communications”/“Enhanced Data ratesfor GSM Evolution”) as well as UMTS/HSPA (“Universal MobileTelecommunications System”/“High Speed Packet Access”) networktechnologies. The standard is developed by the 3GPP (“3rd GenerationPartnership Project”).

As shown in FIG. 1a , the system 100 can include an evolved universalterrestrial radio access network (“EUTRAN”) 102, an evolved packet core(“EPC”) 108, and a packet data network (“PDN”) 101, where the EUTRAN 102and EPC 108 provide communication between a user equipment 104 and thePDN 101. The EUTRAN 102 can include a plurality of evolved node B's(“eNodeB” or “ENODEB” or “enodeb” or “eNB”) or base stations 106 (a, b,c) (as shown in FIG. 1b ) that provide communication capabilities to aplurality of user equipment 104(a, b, c). The user equipment 104 can bea mobile telephone, a smartphone, a tablet, a personal computer, apersonal digital assistant (“PDA”), a server, a data terminal, and/orany other type of user equipment, and/or any combination thereof. Theuser equipment 104 can connect to the EPC 108 and eventually, the PDN101, via any eNodeB 106. Typically, the user equipment 104 can connectto the nearest, in terms of distance, eNodeB 106. In the LTE system 100,the EUTRAN 102 and EPC 108 work together to provide connectivity,mobility and services for the user equipment 104.

FIG. 1b illustrates further detail of the network 100 shown in FIG. 1a .As stated above, the EUTRAN 102 includes a plurality of eNodeBs 106,also known as cell sites. The eNodeBs 106 provides radio functions andperforms key control functions including scheduling of air linkresources or radio resource management, active mode mobility orhandover, and admission control for services. The eNodeBs 106 areresponsible for selecting which mobility management entities (MMES, asshown in FIG. 1c ) will serve the user equipment 104 and for protocolfeatures like header compression and encryption. The eNodeBs 106 thatmake up an EUTRAN 102 collaborate with one another for radio resourcemanagement and handover.

Communication between the user equipment 104 and the eNodeB 106 occursvia an air interface 122 (also known as “LTE-Uu” interface). As shown inFIG. 1b , the air interface 122 provides communication between userequipment 104 b and the eNodeB 106 a. The air interface 122 usesOrthogonal Frequency Division Multiple Access (“OFDMA”) and SingleCarrier Frequency Division Multiple Access (“SC-FDMA”), an OFDMAvariant, on the downlink and uplink respectively. OFDMA allows use ofmultiple known antenna techniques, such as, Multiple Input MultipleOutput (“MIMO”).

The air interface 122 uses various protocols, which include a radioresource control (“RRC”) for signaling between the user equipment 104and eNodeB 106 and non-access stratum (“NAS”) for signaling between theuser equipment 104 and MME (as shown in FIG. 1c ). In addition tosignaling, user traffic is transferred between the user equipment 104and eNodeB 106. Both signaling and traffic in the system 100 are carriedby physical layer (“PHY”) channels.

Multiple eNodeBs 106 can be interconnected with one another using an X2interface 130(a, b, c). As shown in FIG. 1a , X2 interface 130 aprovides interconnection between eNodeB 106 a and eNodeB 106 b; X2interface 130 b provides interconnection between eNodeB 106 a and eNodeB106 c; and X2 interface 130 c provides interconnection between eNodeB106 b and eNodeB 106 c. The X2 interface can be established between twoeNodeBs in order to provide an exchange of signals, which can include aload- or interference-related information as well as handover-relatedinformation. The eNodeBs 106 communicate with the evolved packet core108 via an S1 interface 124(a, b, c). The S1 interface 124 can be splitinto two interfaces: one for the control plane (shown as control planeinterface (S1-MME interface) 128 in FIG. 1c ) and the other for the userplane (shown as user plane interface (S1-U interface) 125 in FIG. 1c ).

The EPC 108 establishes and enforces Quality of Service (“QoS”) for userservices and allows user equipment 104 to maintain a consistent internetprotocol (“IP”) address while moving. It should be noted that each nodein the network 100 has its own IP address. The EPC 108 is designed tointerwork with legacy wireless networks. The EPC 108 is also designed toseparate control plane (i.e., signaling) and user plane (i.e., traffic)in the core network architecture, which allows more flexibility inimplementation, and independent scalability of the control and user datafunctions.

The EPC 108 architecture is dedicated to packet data and is shown inmore detail in FIG. 1c . The EPC 108 includes a serving gateway (S-GW)110, a PDN gateway (P-GW) 112, a mobility management entity (“MME”) 114,a home subscriber server (“HSS”) 116 (a subscriber database for the EPC108), and a policy control and charging rules function (“PCRF”) 118.Some of these (such as S-GW, P-GW, MME, and HSS) are often combined intonodes according to the manufacturer's implementation.

The S-GW 110 functions as an IP packet data router and is the userequipment's bearer path anchor in the EPC 108. Thus, as the userequipment moves from one eNodeB 106 to another during mobilityoperations, the S-GW 110 remains the same and the bearer path towardsthe EUTRAN 102 is switched to talk to the new eNodeB 106 serving theuser equipment 104. If the user equipment 104 moves to the domain ofanother S-GW 110, the MME 114 will transfer all of the user equipment'sbearer paths to the new S-GW. The S-GW 110 establishes bearer paths forthe user equipment to one or more P-GWs 112. If downstream data arereceived for an idle user equipment, the S-GW 110 buffers the downstreampackets and requests the MME 114 to locate and reestablish the bearerpaths to and through the EUTRAN 102.

The P-GW 112 is the gateway between the EPC 108 (and the user equipment104 and the EUTRAN 102) and PDN 101 (shown in FIG. 1a ). The P-GW 112functions as a router for user traffic as well as performs functions onbehalf of the user equipment. These include IP address allocation forthe user equipment, packet filtering of downstream user traffic toensure it is placed on the appropriate bearer path, enforcement ofdownstream QoS, including data rate. Depending upon the services asubscriber is using, there may be multiple user data bearer pathsbetween the user equipment 104 and P-GW 112. The subscriber can useservices on PDNs served by different P-GWs, in which case the userequipment has at least one bearer path established to each P-GW 112.During handover of the user equipment from one eNodeB to another, if theS-GW 110 is also changing, the bearer path from the P-GW 112 is switchedto the new S-GW.

The MME 114 manages user equipment 104 within the EPC 108, includingmanaging subscriber authentication, maintaining a context forauthenticated user equipment 104, establishing data bearer paths in thenetwork for user traffic, and keeping track of the location of idlemobiles that have not detached from the network. For idle user equipment104 that needs to be reconnected to the access network to receivedownstream data, the MME 114 initiates paging to locate the userequipment and re-establishes the bearer paths to and through the EUTRAN102. MME 114 for a particular user equipment 104 is selected by theeNodeB 106 from which the user equipment 104 initiates system access.The MME is typically part of a collection of MMEs in the EPC 108 for thepurposes of load sharing and redundancy. In the establishment of theuser's data bearer paths, the MME 114 is responsible for selecting theP-GW 112 and the S-GW 110, which will make up the ends of the data paththrough the EPC 108.

The PCRF 118 is responsible for policy control decision-making, as wellas for controlling the flow-based charging functionalities in the policycontrol enforcement function (“PCEF”), which resides in the P-GW 110.The PCRF 118 provides the QoS authorization (QoS class identifier(“QCI”) and bit rates) that decides how a certain data flow will betreated in the PCEF and ensures that this is in accordance with theuser's subscription profile.

As stated above, the IP services 119 are provided by the PDN 101 (asshown in FIG. 1a ).

II. eNodeB

FIG. 1d illustrates an exemplary structure of eNodeB 106. The eNodeB 106can include at least one remote radio head (“RRH”) 132 (typically, therecan be three RRH 132) and a baseband unit (“BBU”) 134. The RRH 132 canbe connected to antennas 136. The RRH 132 and the BBU 134 can beconnected using an optical interface that is compliant with commonpublic radio interface (“CPRI”) 142 standard specification. Theoperation of the eNodeB 106 can be characterized using the followingstandard parameters (and specifications): radio frequency band (Band4,Band9, Band17), bandwidth (5, 10, 15, 20 MHz), access scheme (downlink:OFDMA; uplink: SC-OFDMA), antenna technology (downlink: 2×2 MIMO;uplink: 1×2 single input multiple output (“SIMO”)), number of sectors (6maximum), maximum transmission power (60 W), maximum transmission rate(downlink: 150 Mb/s; uplink: 50 Mb/s), S1/X2 interface (1000Base-SX,1000Base-T), and mobile environment (up to 350 km/h). The BBU 134 can beresponsible for digital baseband signal processing, termination of S1line, termination of X2 line, call processing and monitoring controlprocessing. IP packets that are received from the EPC 108 (not shown inFIG. 1d ) can be modulated into digital baseband signals and transmittedto the RRH 132. Conversely, the digital baseband signals received fromthe RRH 132 can be demodulated into IP packets for transmission to EPC108.

The RRH 132 can transmit and receive wireless signals using antennas136. The RRH 132 can convert (using converter (“CONV”) 140) digitalbaseband signals from the BBU 134 into radio frequency (“RF”) signalsand power amplify (using amplifier (“AMP”) 138) them for transmission touser equipment 104 (not shown in FIG. 1d ). Conversely, the RF signalsthat are received from user equipment 104 are amplified (using AMP 138)and converted (using CONV 140) to digital baseband signals fortransmission to the BBU 134.

FIG. 2 illustrates an additional detail of an exemplary eNodeB 106. TheeNodeB 106 includes a plurality of layers: LTE layer 1 202, LTE layer 2204, and LTE layer 3 206. The LTE layer 1 includes a physical layer(“PHY”). The LTE layer 2 includes a medium access control (“MAC”), aradio link control (“RLC”), a packet data convergence protocol (“PDCP”).The LTE layer 3 includes various functions and protocols, including aradio resource control (“RRC”), a dynamic resource allocation, eNodeBmeasurement configuration and provision, a radio admission control, aconnection mobility control, and radio resource management (“RRM”). TheRLC protocol is an automatic repeat request (“ARQ”) fragmentationprotocol used over a cellular air interface. The RRC protocol handlescontrol plane signaling of LTE layer 3 between the user equipment andthe EUTRAN. RRC includes functions for connection establishment andrelease, broadcast of system information, radio bearerestablishment/reconfiguration and release, RRC connection mobilityprocedures, paging notification and release, and outer loop powercontrol. The PDCP performs IP header compression and decompression,transfer of user data and maintenance of sequence numbers for RadioBearers. The BBU 134, shown in FIG. 1d , can include LTE layers L1-L3.

One of the primary functions of the eNodeB 106 is radio resourcemanagement, which includes scheduling of both uplink and downlink airinterface resources for user equipment 104, control of bearer resources,and admission control. The eNodeB 106, as an agent for the EPC 108, isresponsible for the transfer of paging messages that are used to locatemobiles when they are idle. The eNodeB 106 also communicates commoncontrol channel information over the air, header compression, encryptionand decryption of the user data sent over the air, and establishinghandover reporting and triggering criteria. As stated above, the eNodeB106 can collaborate with other eNodeB 106 over the X2 interface for thepurposes of handover and interference management. The eNodeBs 106communicate with the EPC's MME via the S1-MME interface and to the S-GWwith the S1-U interface. Further, the eNodeB 106 exchanges user datawith the S-GW over the S1-U interface. The eNodeB 106 and the EPC 108have a many-to-many relationship to support load sharing and redundancyamong MMES and S-GWs. The eNodeB 106 selects an MME from a group of MMESso the load can be shared by multiple MMES to avoid congestion.

III. Intelligent LTE Radio Access Network

FIG. 3 illustrates an exemplary system 300, according to someimplementations of the current subject matter. The system 300 can beimplemented as a centralized cloud radio access network (“C-RAN”). Thesystem 300 can include at least one intelligent remote radio head(“iRRH”) unit 302 and an intelligent baseband unit (“iBBU”) 304. TheiRRH 302 and iBBU 304 can be connected using Ethernet fronthaul (“FH”)communication 306 and the iBBU 304 can be connected to the EPC 108 usingbackhaul (“BH”) communication 308. The user equipment 104 (not shown inFIG. 3) can communicate with the iRRH 302.

In some implementations, the iRRH 302 can include the power amplifier(“PA”) module 312, the radio frequency (“RF”) module 314, LTE layer L1(or PHY layer) 316, and a portion 318 of the LTE layer L2. The portion318 of the LTE layer L2 can include the MAC layer and can furtherinclude some functionalities/protocols associated with RLC and PDCP, aswill be discussed below. The iBBU 304 can be a centralized unit that cancommunicate with a plurality of iRRH and can include LTE layer L3 322(e.g., RRC, RRM, etc.) and can also include a portion 320 of the LTElayer L2. Similar to portion 318, the portion 320 can include variousfunctionalities/protocols associated with PDCP. Thus, the system 300 canbe configured to split functionalities/protocols associated with PDCPbetween iRRH 302 and the iBBU 304.

In some implementation, the system 300 can implement carrier aggregation(“CA”) and coordinated multipoint (“CoMP”) transmission features. The CAand CoMP features have been discussed in the 3GPP standards for 4GLTE-Advanced, Releases 10 and 11, respectively. Both features aredesigned to increase data throughput rate and designed to work with 4GLTE-Advanced. The following is a brief summary of each of thesefeatures.

A. Carrier Aggregation

The CA or channel aggregation enables multiple LTE carriers to be usedtogether to provide high data rates that are required for 4GLTE-Advanced. These channels or carriers can be in contiguous elementsof the spectrum, or they may be in different bands. The carriers can beaggregated using contiguous intra-band carrier aggregation,non-contiguous intra-band carrier aggregation, and inter-bandnon-contiguous carrier aggregation. In the contiguous intra-band carrieraggregation, carriers are adjacent to one another and aggregated channelcan be considered by a user equipment as a single enlarged channel froma radio frequency (“RF”) viewpoint and only one transceiver is requiredwithin the user equipment (usually, more transceivers are required wherethe channels are not adjacent). In the non-contiguous intra-band carrieraggregation typically requires two transceivers and a multi-carriersignal is not treated as a single signal. In the inter-bandnon-contiguous carrier aggregation, multiple transceivers are requiredto be present within a single user equipment, which can affect cost,performance and power. Additionally, this aggregation technique canrequire reduction in intermodulation and cross modulation from the twotransceivers. When carriers are aggregated, each carrier can be referredto as a component carrier. There exist two categories of componentcarriers: a primary component carrier (i.e., main carrier in any group;there are a primary downlink carrier and an associated uplink primarycomponent carrier), and a secondary component carrier (there are one ormore secondary component carriers). Association between downlink primaryand corresponding uplink primary component carriers is cell specific.

When LTE carrier aggregation is used, it is necessary to be able toschedule the data across the carriers and to inform the terminal of theDCI rates for different component carriers. Cross-carrier scheduling canbe achieved individually via RRC signaling on a per component carrierbasis or a per user equipment basis. When no cross-carrier scheduling isarranged, the downlink scheduling assignments can be achieved on a percarrier basis. For the uplink, an association can be created between onedownlink component carrier and an uplink component carrier. Whencross-carrier scheduling is active, the physical downlink shared channel(“PDSCH”) on the downlink or the physical uplink shared channel(“PUSCH”) on the uplink is transmitted on an associate component carrierother than the physical downlink control channel (“PDCCH”), the carrierindicator in the PDCCH provides the information about the componentcarrier used for the PDSCH or PUSCH. The PDSCH is the main data bearingchannel allocated to users on a dynamic basis and that carries data intransport blocks (“TB”) that correspond to a MAC packet data unit(“PDU”), which are passed from the MAC layer to the PHY layer once pertransmission time interval (“TTI”) (i.e., 1 ms). The PUSCH is a channelthat carries user data and any control information necessary to decodeinformation such as transport format indicators and MIMO parameters. ThePDCCH is a channel that carries resource assignment for user equipments,which are contained in a downlink control information (“DCI”) message.

There exist five deployment scenarios for CA. In the first scenario,cells (e.g., F1 and F2 cells) can be co-located and overlaid, therebyproviding nearly the same coverage. Both layers provide sufficientcoverage and mobility can be supported on both layers. In the secondscenario, cells F1 and F2 can be co-located and overlaid, however, F2cells have smaller coverage due to larger path losses, where only F1cells provide sufficient coverage and F2 cells are used to improvethroughput. Here, mobility is performed based on F1 cells coverage. Inthe third scenario, F1 and F2 cells are co-located and overlaid,however, F2 cells have smaller coverage due to larger path losses, whereonly F1 cells provide sufficient coverage and F2 cells are used toimprove throughput. Here, mobility is based on F1 cells coverage. In thefourth scenario, F1 cells provide macro coverage and F2 cells' remoteradio heads are used to improve throughput at hot spots, where mobilityis again performed based on F1 cells coverage. In the fifth scenario,which is similar to the second scenario, frequency selective repeatersare deployed so that coverage is extended for one of the carrierfrequencies. It is expected that F1 and F2 cells of the same eNodeB canbe aggregated where coverage overlaps.

B. Coordinated Multipoint Transmission

The CoMP transmission feature is used to send and receive data to andfrom a user equipment from several points to ensure the optimumperformance is achieved even at cell edges. CoMP enables dynamiccoordination of transmission and reception over a variety of differentbase stations to improve overall quality for the user as well as improveutilization of the network. CoMP further requires close coordinationbetween a number of geographically separated eNodeBs to provide jointscheduling and transmissions, joint processing of received signals,thereby allowing a user equipment at the edge of a cell to be served bytwo or more eNodeBs so as to improve signal reception/transmission andincrease throughput.

There exist four deployment scenarios for CoMP. The first scenarioinvolves a homogeneous network with intra-site CoMP. The second scenarioalso involves a homogeneous network but with high transmission powerRRHs. The third scenario involves a heterogeneous network with low powerRRHs within a macro cell coverage, where transmission/reception pointscreated by the RRHs have different cell identifiers as the macro cell.The fourth scenario involves a heterogeneous network with low power RRHswithin a macro cell coverage, where transmission/reception pointscreated by the RRHs have the same cell identifiers as the macro cell.

The CoMP feature uses the following three scheme: coordinatedscheduling/beamforming (“CS/CB”), joint processing (“JP”), and dynamicpoint selection (“DPS”). The CS/CB scheme coordinates steering of beamsformed by different transmission points serving different userequipments. A user equipment can be semi-statically served by only onetransmission point and data does not need to be passed around fromtransmission point to transmission point. The JP scheme involvessimultaneous data transmission from multiple transmission points to asingle user equipment or multiple user equipments in a time-frequencyresource. JT scheme requires different transmission points to becompletely synchronized in terms of the timing, TB format, PRBallocation and reference signals when transmitting data to a particularuser equipment. The user equipment need not be aware that thetransmission is coming from multiple transmission points. This schemecan require very tight coordination between schedulers or a singlescheduler entity to achieve the required level of synchronization. TheDPS scheme (a variant of the JT scheme) involves data transmission fromone transmission point in a time-frequency resource, where thetransmission point may change from one subframe to another.

C. Ethernet-Based Front Haul in Intelligent LTE RAN

FIG. 4a illustrates an exemplary system 400, according to someimplementations of the current subject matter. The system 400 can beconfigured to implement 4G LTE-Advanced features, including carrieraggregation feature. The system 400 can include an intelligent basebandunit (“iBBU”) 402, a primary cell (“Pcell”) intelligent remote radiohead 404 and one or more secondary cells (“Scell”) intelligent remoteradio heads 406. In LTE CA, the Pcell is the serving cell where the UEhas an RRC connection with the radio access network. Pcell can only bechanged through a successful execution of a handover procedure. Scell isa secondary cell that can be added/removed from the configured cellslist when the UE moves into/out of its coverage area. The configurationof a Scell is done by RRC based on mobility measurement events triggeredin the UE and sent to RRC.].

As shown in FIG. 4a , each iRRH 404 and 406 can both include the LTElayer 1 (i.e., the PHY layer) and have LTE layer 2 (i.e., MAC, PDCP,RLC) split among themselves as well as iBBU 402. The iRRH 404 caninclude a PHY layer 412, a MAC layer 414, a scheduler-Pcell component416, a master RLC component 418, a RLC status component 420, aPDCP-security component 422, and a BSR component 424. Similarly, theiRRH 406 can include a PHY layer 411, a MAC layer 413, a scheduler-Scellcomponent 415, a slave RLC component 419, a RLC status component 421, aPDCP-security component 423, and a BSR component 425. The iBBU 402 caninclude a buffer management component 432, a PDCP-SN component 434, aPDCP-RoHC component 436, a VAS component 438, an RRC component 440, anda GTP component 442.

The buffer management component 432 can implement use of bufferoccupancy reports that can be received from the iRRH's to control flowof user data to the Pcell and/or Scell in order to enable in sequencedelivery of the data to the user equipment. The PDCP-SN component 434can perform sequence numbering of the PDCP service data units (“PDCPSDUs”). The PDCP robust header compression (“PDCP-RoHC”) component 436can perform IP header compression for voice-over-LTE service flows. Thevalue added services (“VAS”) component 438 can provide applicationintelligence in the eNodeB by performing shallow packet inspection anddeep packet inspection of data flows. This component can also determinehow a particular data flow can be treated. A shallow packet inspection(“SPI”) can be performed by inspecting one or more headers of the datapacket to determine information associated with the data packet. Forexample, the shallow packet inspection can inspect an IP header of thedata packet in order to determine the source IP address of the datapacket. In some implementations, based on the results of the shallowpacket inspection, a deep packet inspection (“DPP”) can be performed byexamining other layers of the data packet. In some implementations, thepayload of a data packet can be inspected to determine what resourceblocks should be assigned to the data packet.

The iRRH 404 and the iRRH 406 can communicate with one another via aninter-iRRH interface, which can be a direct connection 452, or aconnection that can be shared with a fronthaul connection 458. The iRRH404 can communicate with the iBBU 402 using the fronthaul (“FH”)connection 458 and the iRRH 406 can communicate with the iBBU 402 usingFH connection 464.

In some implementations, the iBBU 402 can provide a centralized remoteradio resource control (“RRC”) using RRC component 440, therebyeliminating a need for a long-delay inter-RRC coordination and providingan ability to configure LTE layer 2 in iRRH 404 and 406. This capabilitycan be implemented as part of the coordinated multipoint transmissionfeature, as discussed below.

As shown in FIG. 4a , the functionalities associated PDCP protocol canbe split among the iBBU 402, the iRRH 404, and the iRRH 406. ThePDCP-ROHC 436 (where ROHC refers to robust header compression protocolthat is used to compress packets) and the PDCP-SN 434 (where SN refersto sequence numbering) together with buffer management component 432 iniBBU 402 can be referred to as PDPC-upper, and PDCP-security 422, 423 iniRRH 404, 406, respectively, can be referred to as PDCP-lower. By havingPDCP-upper in the iBBU 402 and PDCP-lower in iRRH 404, 406, the PDCPfunctionalities can be centralized to handle the ROHC and sequencenumbering functions by the iBBU 402, and ciphering functions by the iRRH(which refer to known functionalities of the PDPC). In someimplementations, the PDCP-upper in iBBU 402 can also handle coordinationof data flows to the schedulers in the iRRHs.

Further, by using PDCP-upper and PDCP-lower, flow control between iBBU402 and iRRH 406 can be provided. The flow control can depend on anestimated data rate for the bearer. For example, on the downlink 462,the PDCP-upper can send compressed and numbered packets to Pcell iRRH404 and Scell iRRH 406 in proportion based on buffer occupancy level andestimated data rate from the reports provided by PDCP-lower. In someimplementations, the PDCP-lower can generate a report of a bufferoccupancy level. This report can be generated periodically, uponrequest, automatically, manually, and/or on for any period of time.Based on the report, the PDCP-upper can estimate a buffer draining ratebased on consecutive buffer occupancy reports (e.g., two reports), atime that elapsed between the reports and the additional data that wassent to the buffer between the reports.

The iBBU 402 can include a buffer management function 432 to support thein-sequenced delivery of PDCP packet data units (“PDCP PDU”) and supportvalue added services (“VAS”) multi-queue implementation for the defaultbearer. The buffer management function 432 can detect buffer stalling inthe Scell 406 and trigger a redirection of the staled PDCP PDU packetsto the Pcell 404. PDCP-lower can detect outdated packets and discardthem from its buffer. The in-sequenced delivery of PDCP PDUs can referto a requirement for data flow transmitted in RLC acknowledged andunacknowledged modes. VAS multi-queue implementation can enableprioritization of data flows within the default bearer. In someimplementations, the detection of buffer stalling can be based on anestimated buffer drain rate that can be derived from the bufferoccupancy reports received from the PDCP-lower.

In some implementations, to perform redirection of packets, thePDCP-upper can tag each packet data unit with time-to-live information(which can refer to an amount of time before a data packet expires).Then, the PDCP-lower can remove the packet from its buffer when thetime-to-live timer for that packet expires and inform the PDCP-upper ofthe deleted packet's number. The PDCP-upper can decide whether to resendthe deleted packet to the same PDCP-lower and/or redirect the deletedpacket to a PDCP-lower of another iRRH. The discarding of packets can beperformed on the Pcell and/or the Scell and the packets can beredirected toward the Pcell and/or the Scell.

In some implementations, the RLC protocol handling can be split betweeniRRH 404 and iRRH 406, where the iRRH 404 can include a master RLCcomponent 418 and the iRRH 406 can include a slave RLC component 419.The master RLC component 418 can allocate an RLC PDU sequence number tothe slave RLC component 419, thereby centralizing RLC PDU sequencenumbering process. In the current subject matter system, each RLC entitycan maintain a list of unacknowledged PDUs that it has transmitted andthus, handle the ARQ procedures for only those unacknowledged PDUs thatit has transmitted. This is because the RLC entity might not be aware ofother PDUs that can be sent by other entities and/or might not have theoriginal data to handle the re-transmissions of the unacknowledged PDUs.In some implementations, an RLC ARQ status PDU, which can be sent from auser equipment at a rate of once very few 10's of a millisecond, can beshared between the two RLC entities over the inter-iRRH interface, i.e.,the direct connection 452 and/or a connection shared with fronthaul 458.In some implementations, the physical connection for this inter-iRRHinterface can either be direct and/or through a L2 Ethernet switch. Insome implementations, the above inter-iRRH interface can leverageindustry standard stream control transport protocol (“SCTP”) over IP.The application layer information exchange can be based on aninter-process communication protocols.

In some implementations, the inter-iRRH interface 452 can provide a lowlatency interface for sharing of the RLC status information PDUs as wellas any other information between iRRHs 404 and 406. Channel stateinformation (“CSI”), acknowledgement/non-acknowledgement (“ACK/NACK”)signaling, precoding matrix indicator (“PMI”), and rank indicator (“RI”)that are received by the Pcell iRRH 404 can be forwarded over theinter-iRRH interface 452 for sharing with an Scell scheduler 415 via thefronthaul or direct gigabit Ethernet (“GE”) connection. This informationcan be available to the Scell scheduler on the same sub-frame that itwas sent in order not to incur any impact the H-ARQ RTT, which can betargeted to be 8 ms. The Scell scheduler can also accommodate longerdelay in obtaining the H-ARQ feedback and can impact H-ARQ round triptime on the Scell.

In some implementations, the inter-iRRH interface 452 can be used by theScell iRRH 406 to inform the Pcell iRRH 404 which PUCCH resource toexpect the arrival of the H-ARQ ACK/NACK feedback for a packet sent onthe Scell (where the allocation of PUCCH resources is defined in the3GPP Standards for 4G LTE). By way of a non-limiting example, thescheduler can be designed to determine which user equipment to schedule2 ms in advance of when the data is transmitted over the air. The H-ARQACK/NACK can be sent from the user equipment 4 ms after the data hasbeen received. Thus, to ensure the Pcell iRRH 404 is informed of thePUCCH resource usage before the downlink H-ARQ ACK/NACK informationarrives from the user equipment, an exemplary one-way latency for theinter-iRRH interface 452 might not be more than 4 ms. As can beunderstood, the above is provided as an illustrative non-limiting,exemplary implementation of the current subject matter system. It shouldbe further understood that the current subject matter system is notlimited to specific data scheduling parameters and/or particular latencyassociated with transmission of data, and can be designed using anyscheduling, latency and/or any other parameters.

In some implementations, the inter-iRRH transport 456 can be shared withthe fronthaul and switched at the iBBU 402 and/or a physical directconnection 452 between the iRRHs 404, 406 using a gigabit Ethernetinterface. When the inter-iRRH interface is configured as a switchedconnection 456 across the fronthaul, the fronthaul latency can be basedon a very low latency transport such as in the case when the iBBU 402and the iRRHs 404 and/or 406 are collocated and/or when based on LOSwireless transport such as MW, mmWave, FSO, when the iRRH's aregeographically separated.

D. Coordinated Multipoint Transmission in Intelligent LTE RAN

In some implementations, the current subject matter system can beconfigured to implement 4G LTE-Advanced features, including coordinatedmultipoint transmission (“CoMP”) feature. FIGS. 4b-c illustrateexemplary known dynamic point selection (“DPS”) (FIG. 4b ) andcoordinated scheduling/beamforming (“CS/CB”) (FIG. 4c ) schemes that canbe implemented as part of the CoMP feature. The DPS scheme can refer toa scheme where the transmission point is varied according to changes inchannel and interference conditions. The CS/CB scheme can allowcoordination of scheduling decisions of neighboring points to reduceinterference. These schemes can include point blanking/muting, i.e.,whereby one or more transmission points can be turned off in order todecrease interference. These schemes can reduce interference and improvethe LTE cell-edge performance. Further, in some implementations, usingthese schemes, the user equipment can be scheduled to receive data fromtwo points while a third point is muted and/or the user equipment can bescheduled to receive data only from one point where the other one ormore points coordinate scheduling and/or are muted to reduceinterference.

FIG. 4b illustrates an exemplary implementation of the DPS scheme.According to this scheme, a user equipment 479 can be located within acoordination area 472 of two points 473 and 477, where each has cellareas 471 and 475, respectively. The user equipment 479 can be served byone of the points 473, 477 having better channel conditions. FIG. 4cillustrates an exemplary implementation of the CS/CB scheme. Accordingto this scheme, a user equipment 489 can be located within acoordination area 482 of two points 483 and 487, where each has cellareas 481 and 485, respectively. In this scheme, beam forming andscheduling for the user equipment can be coordinated by the network toavoid interference 486 that can be generated by one of the points (e.g.,point 487 as shown in FIG. 4c ).

In some implementations, the operation of the current subject mattersystem using dynamic point selection scheme can be as follows. The userequipment can connect to a serving cell using an RRC connection setupand configured for transmission (e.g., TM10 transmission mode). Once theconnection is setup, the uplink connection can remain on the servingcell and can change with the handover procedure. RRC can configureinitial downlink transmission points (“TP”) based on known referencesignal received power (“RSRP”) and reference signal received quality(“RSRQ”) measurements, which refer to parameters of a strength/qualityof a reference signal (“RS”) of a cell as determined by a user equipmentwhen it moves from cell to cell and performs cell selection/reselectionand handover. The RRC can then configure channel state informationreference signal (“CSI-RS”) process per transmission point for channelstate information (“CSI”) reporting, including precoding matrix forphysical downlink shared channel (“PMI”), which can be referred to as ameasurement set. Then, the RRC can configure enhanced physical downlinkcontrol channel (“ePDCCH”) per transmission point, which can be referredas a cooperation set. Then, each CoMP transmission point can perform itsown scheduling and send an allocation over ePDCCH, thereby providingresource and link adaptation information. The current transmission pointserving the user equipment can decode physical uplink control channelinformation sent by user equipment to the serving cell to extract HARQand CSI feedback information. Based on that information, the currenttransmission point can determine the resource allocation for the userequipment. The iBBU can preposition data at all transmission points inthe cooperation set for fast switching of CoMP transmission points.Then, only the RLC context can be transferred from a previoustransmission point to the current transmission point during transmissionpoint switching. Based on the CSI feedback, the current transmission caninform RRC/RRM components in the iBBU to allow these components to makedecisions on transmission point switching and transmission pointaddition/dropping from the cooperation and measurement sets as well asserving cell change (e.g., during handover). Further, the RRC/RRMcomponents can then select an active transmission point based on a loadlevel of each transmission point in the cooperation set as well as basedon the CSI.

In some implementations, the operation of the current subject mattersystem using the coordinated scheduling/beamforming scheme can be asfollows. At lower loads, fractional frequency reuse (“FFR”) mechanismcan be activated to provide a blanking mechanism and/or to lower thepower of physical resource blocks (“PRBs”) in scheduling coordinationwith the serving transmission point (as discussed in 3GGP standards for4G LTE, and in particular its Release 8 discussing a dynamic inter-cellinterference coordination (“ICIC”)). For time division duplex (“TDD”)and at high traffic loads, the uplink sounding reference signal CULSRS″) in the user equipment can be configured and the transmissionpoints in the cooperation set can be informed to measure channel stateinformation of the user equipment. Coordinated beam forming can beachieved using semi-static time and spatial domain coordination betweenthe transmission points in the cooperation set. For frequency divisionduplex (“FDD”) and at high traffic loads, the PMI feedback for eachCSI-RS process can be configured. In this case, the PUCCH can be decodedat each transmission point for channel state information reported by theuser equipment. Here, the coordinated beam forming can be also achievedusing semi-static time and spatial domain coordination between thetransmission points in the cooperation set and based on channel stateinformation reports at each transmission point.

In some implementations, in a single scheduler implementation, it ispossible that no transmission gap can be present when the transmissionpoint is switched. In some exemplary, non-limiting implementations, in adistributed scheduling solution, the inter-iRRH one-way latency may beless than 200 ms, which can allow for transmission point switching witha gap of two transmission time intervals (“TTI”). Other values one-waylatencies are possible and may or may not be noticeable.

IV. Call Flow Procedures in Intelligent LTE RAN

The following description along with FIGS. 5a-8d provide a discussion ofexemplary call flow procedures using the current subject matter system,including the RRC procedures, such as, an inter-eNodeB handoverprocedure (as shown in FIGS. 5a-5d ), an intra-eNodeB handover procedure(as shown in FIGS. 6a-6c ), an RRC connection establishment procedure(as shown in FIGS. 7a-7h ), and an RRC connection re-establishmentprocedure (as shown in FIGS. 8a-8d ). It should be noted that theprocedures shown in FIGS. 5a-8d are provided for exemplary, non-limitingand/or illustrative purposes. It is not intended that the currentsubject matter system be limited to the shown call flow procedures.Other procedures and/or variations of the illustrated procedures can beused by the current subject matter system.

In some implementations, to optimize RRC procedures for a call flow, oneor more of the following optimization techniques can be used:

-   -   combining of multiple sequential Layer 1 and/or Layer 2        configuration messages into one;    -   piggybacking of RRC messages with Layer 1 and/or Layer 2        configuration messages, if possible;    -   providing iRRH with intelligence to allow iRRH to determine when        to start sending user plane data when it receives UL RRC        acknowledgement messages; and/or    -   redistributing Layer 2 functionalities between the iBBU and iRRH        to achieve the best possible performance.

In some implementations, using the above procedures, the current subjectmatter system can significantly reduce latency associated withcommunications in the LTE systems.

A. Handover Procedures in the Control Plane

1. Inter-eNodeB Handover Procedures

FIGS. 5a-5d illustrate an exemplary inter-eNodeB handover procedures inthe control plane, according to some implementations of the currentsubject matter. FIG. 5a illustrates an exemplary system 500 that caninclude an iBBU 504 and an iBBU 506 that can communicate with an evolvedpacket core (“EPC”) 502 using S1 connections 531, 533, respectively. TheiBBUs 504 and 506 can communicate with one another using an X2connection 535. One of the iBBUs 504, 506 can be a source (i.e., fromwhere a communication can originate) and the other can be a target(i.e., a recipient of the communication). The system 500 can alsoinclude a plurality of iRRHs 508, 510, 512, and 514. As discussed above,the iRRHs can be connected with to their respective iBBUs via fronthaul(“FH”) connections. For example the iRRH 508 can be connected to theiBBU 504 via FH connection 541; the iRRH 510 can be connected to theiBBU 504 via FH connection 543, the iRRH 512 can be connected to theiBBU 506 via FH connection 545; and iRRH 514 can be connected to theiBBU 506 via FH connection 547. A plurality of user equipments 516, 518,520, and 522 can communicate over-the-air with the iRRH 508, 510, 512,and 514, respectively.

In some implementations, the system 500 can allow for various handoverscenarios, which can include a macro-to-macro scenario, micro-to-microscenario, micro-to-macro scenario, and macro-to-micro scenario. In someimplementations, in the macro-to-macro scenario, the user equipment 520can directly communicate with the iBBU 506. In this case, the iBBUs canbe centralized, which can cause the X2 interface 535 to have zerolatency. In alternate implementations, the macro iRRH can be collocatedwith the iBBU and thus, the two can be connected using a very lowlatency FH connection, thereby making an impact on HO performance causedby the FH latency negligible.

The micro-to-micro scenario can involve a communication between two iRRH510, 512. In this case, both the source and the target cells (i.e.,iBBUs 504, 506) can have high-latency FH connections.

The micro-to-macro scenario can involve a communication between userequipment 516 and iBBU 506. In this case, any communications between theuser equipment 516 and the source micro cell can involve at least onehigh-latency FH communication.

The macro-to-micro scenario can involve communication between userequipment 522 and iRRH 514. In this case, any communications between theuser equipment 522 and the target micro cell can involve at least onehigh-latency FH communication.

FIG. 5b illustrates exemplary handover procedures for a source eNodeB,according to some implementations of the current subject matter. Thecommands or messages exchanged during the handover procedures arebetween a user equipment RRC 551, a radio resource management module 553(located at an eNodeB), a eNodeB's RRC module (RRC Cell) 555, an S1application interface (S1AP (located at eNodeB)) 557, a PDCP layer(located at eNodeB) 559, and GPRS Tunneling Protocol (“GTP”) Manager(GTP Mgr (located at eNodeB)) 561.

When looking from the source eNodeB perspective, there can be twomessages that traverse a FH connection during the handover which can addto the duration of the procedure: one can be a measurement result (“MeasResult”) coming from the user equipment, which can trigger a handoverpreparation in the target cell and the second can be a handover command(“Handover Command”) to the user equipment coming from the source eNodeBto the user equipment to inform the user equipment to switch over to thetarget cell. These messages can be RRC messages, which cannot be avoidedand can delineate the handover control plane latency at the sourceeNodeB. Between these messages, another message can be exchanged, whichcan indicate that a handover is required (“Handover Required”). Thismessage can be directed from the source eNodeB to the target eNodeB andcan traverse the S1/X2 interface(s) with an equivalent of two links, onefor each eNodeB. Additionally, a handover command (to user equipment)(“Handover Command (to UE)”) message can be originated from the targeteNodeB and can also traverse the S1/X2 interface with an equivalent oftwo links, one for each eNodeB. There are no other layer 1 and/or layer2 configuration message(s) that traverse the fronthaul connection andprevent sending of the “Handover Command (to UE)” message. The “eNBStatus Transfer Request,” “eNB Transfer Response” and “eNB StatusTransfer” messages are exchanged with the RRC-UE 55 to provide thesource eNodeB status. Once that information is provided, a known “UEContext Release Procedure” can be initiated with “UE Context ReleaseCommand” and can be completed with “UE Context Release Complete”messages.

If the source eNodeB is a macro cell and its iRRH is co-located with theiBBU, then the Meas Result and Handover Command (to UE) messages can goover a very low latency the FH connection, thereby making the impact oftransmission of these messages negligible. The Handover Required messagegoing over the S1/X2 interface might not add more latency to thehandover procedure when compared to the handover procedure based on thedistributed deployment of the eNodeB.

However, if the iBBU of the source and the target eNodeB are collocatedat a central office (“CO”), then the FH connection latency can affectthe connection, with the latency on the S1 or X2 interface beinginsignificant. Thus, the FH latency can be more than offset by the zerolatency on the S1/X2. A reduction equivalent to two links can beachieved.

FIG. 5c illustrates exemplary handover procedures for a target eNodeB,according to some implementations of the current subject matter. Thecommands or messages exchanged during the handover procedures arebetween a user equipment RRC 563, a radio resource management module 565(located at the target eNodeB), S1 application interface (S1AP (locatedat the target eNodeB)) 567, radio link control/MAC layer (located at thetarget eNodeB) 569, a PDCP layer (located at the target eNodeB) 571, andGTP Manager (GTP Mgr (located at eNodeB)) 573.

On the target eNodeB, after receiving a handover request from a sourceeNodeB, the current call flow can have three pairs of request/responsemessages traversing the fronthaul before the handover requestacknowledge message is sent back to the source eNodeB. These messagescan include: “CRNTI Request/CRNTI Response,” “RLC/MAC Config/RLC/MACConfig response”, and “PDCP Config/PDCP Config Response,” which can belayer 1 and/or layer 2 configuration messages. This part of the callflow can be considered as the handover preparation phase. Similar toFIG. 5b , target eNodeB status transfer information messages can beexchanged with the RRC-UE 563 and subsequent to the exchange of thisinformation, a known random access channel (“RACH”) procedure can beperformed. In some implementations, these pairs of three layer 1 and/orlayer 2 configuration messages can be combined into one layer 2 “ConfigRequest”/“L2 Config Response” pair. Thus, only two messages would haveto traverse the fronthaul during this handover preparation phase.

Once the user equipment has switched over to the target eNodeB, twoadditional messages can traverse the fronthaul before the target eNodeBstarts sending data to the user equipment. These can include:“RRCConnectionReconfigurationComplete” and “Send DL Data to UE.” Thesecan also be optimized by giving the PDCP entity in the iRRH anintelligence to know when the “RRCConnectionReconfigurationComplete” isreceived and start sending data without being instructed by the RRCcomponent. In some implementations, both messages can be eliminated fromgating the start of data transfer.

FIG. 5d illustrates an exemplary optimized call flow for the S1-basedhandover in the target eNodeB, according to some implementations of thecurrent subject matter. FIG. 5d is similar to FIG. 5c and includes someof the same components which are used to exchange commands or messages(i.e., the user equipment RRC 563, a radio resource management module565, S1AP 567, and GTP Manager 573). However, as shown in FIG. 5d , theradio link control/MAC layer and a PDCP layer have been combined into asingle component 575 and a VAS component 577 has been added.

Similar to the handover procedures discussed in connection with thesource eNodeB (as shown in FIG. 5b ), if the target eNodeB is a macrocell and its iRRH is co-located with the iBBU, then there can be nopenalty on the handover procedure due to the low latency fronthaul. Insome exemplary implementations, varying degrees of latency on thefronthaul can affect inter eNodeB handover performance.

2. Intra-eNodeB Handover

FIGS. 6a-6d illustrate an exemplary intra-eNodeB handover procedures inthe control plane, according to some implementations of the currentsubject matter. FIG. 6a illustrates an exemplary system 600 that caninclude an iBBU 604 that can communicate with an evolved packet core(“EPC”) 602 using an S1 connection 631. The system 600 can also includeiRRHs 608 and 610. As discussed above, the iRRHs 608, 610 can beconnected with to the iBBU 604 via fronthaul (“FH”) connections. Forexample, the iRRH 608 can be connected to the iBBU 604 via FH connection641; the iRRH 610 can be connected to the iBBU 604 via FH connection643. A plurality of user equipments 616, 618, 620, and 622 cancommunicate over-the-air with the iRRH 608 and 610.

In some implementations, the system 600 can allow for various handoverscenarios, which can include a macro-to-macro scenario, micro-to-microscenario, micro-to-macro scenario, and macro-to-micro scenario. In someimplementations, in the macro-to-macro scenario, the iBBU 604 can becentralized (having higher latency on the fronthaul) or a macro iRRH canbe collocated with the iBBU 604 (having a low latency on the fronthaul).In this scenario, an impact to handover performance caused by thefronthaul latency can be negligible.

In the micro-to-micro scenario, both source and target cells can havehigh latency fronthaul connections. In this case, any handoversinvolving a micro cell can involve an inter-eNodeB handover withinter-eNodeB control messages traversing the S1 or X2 links with anassociated latency impact.

In the micro-to-macro scenario, any communications between userequipment and a source micro cell can involve at least one high latencyfronthaul link. Similar to the micro-to-micro scenario, latency canimpact any inter-eNodeB handover that can involve inter-eNodeB controlmessages traversing S1 or X2 links.

In the macro-to-micro scenario, any communications between userequipment and the target micro cell can involve at least one highlatency fronthaul link. This scenario is also similar to themicro-to-micro and micro-to-macro scenarios.

In some implementations, the intra-eNodeB handover can be similar to X2(inter-eNodeB) handover. In this case, as shown in FIG. 6b , an X2APmodule 639 can route messages meant for cells belonging to the sameeNodeB. Thus, no delay is incurred in connection with the internal X2interface. FIGS. 6b-c illustrate exemplary call flows for the X2-basedhandover procedures in the source and the target eNodeB, respectively.

FIG. 6b illustrates exemplary X2-based handover procedures for a sourceeNodeB, according to some implementations of the current subject matter.The commands or messages exchanged during the handover procedures arebetween a user equipment RRC 633, a radio resource management module 635(located at an eNodeB), a eNodeB's RRC module (RRC Cell) 637, an X2application interface (X2AP (located at eNodeB)) 639, a PDCP layer(located at eNodeB) 641, and GTP Manager (GTP Mgr (located at eNodeB))643.

In some implementations, the number of messages traversing the fronthaulcan similar to the number of messages traversing the fronthaul in theinter-eNodeB handover procedures, as discussed in FIG. 5b above.However, if the source eNodeB is a micro cell, two additionalmessages—“Handover Request” and “Handover Request Ack” can traverse theS1/X2 interface with similar link latency in the fronthaul, as discussedabove. As such, the fronthaul latency can be offset by a zero latency inthe intra-eNodeB handover.

If the source eNodeB is a macro cell and its iRRH is co-located with theiBBU, then the “Meas Result” and “Handover Command (to UE)” messages cantraverse the fronthaul with a low latency, thereby making the latencyimpact substantially negligible.

FIG. 6c illustrates exemplary X2-based handover procedures for a targeteNodeB, according to some implementations of the current subject matter.The commands or messages exchanged during the handover procedures arebetween a user equipment RRC 645, a radio resource management module(located at the target eNodeB) 647, X2 application interface (X2AP(located at the target eNodeB)) 649, RLC/MAC layer (located at thetarget eNodeB) 651, a PDCP layer (located at the target eNodeB) 653, andGTP Manager (GTP Mgr (located at eNodeB)) 655.

The X2-based handover procedures for the target eNodeB can be similar tothe S1-based handover procedures for the target eNodeB, as discussedabove in connection with FIG. 5c . Additionally, if eNodeB is a microcell, two additional messages—“Handover Request” and “Handover RequestAck” can traverse the S1/X2 interface with similar link latency, asdiscussed above. As such, there is no increase in intra-eNodeB handovercontrol plane latency due to the fronthaul in the target eNodeB duringthe handover preparation.

If the target eNodeB is a macro cell and its iRRH is co-located with theiBBU, then the “L2 Config Request/L2 Config” messages can traverse thefronthaul with a low latency, thereby making the overall latency impactsubstantially negligible.

B. Handover Procedures in the User Plane

In the user-plane, key performance indicator can include a transmissiongap starting at the time the user equipment is informed to switch to anew cell to the time when data can start flowing again. The downlink(“DL”) and uplink (“UL”) user-plane handover procedures can be differentand are discussed in the following sections.

1. Handover Procedures in the User Plane on the Downlink

The DL user-plane performance impact can be based on a number ofmessages that can traverse the fronthaul thereby gating the start of thedownlink data transfer over the air. The downlink user-plane performancecan be impacted if the data forwarding procedure takes too long andforces the target eNodeB to wait for data to be available to send whilethe user equipment has already indicated that it is ready to receive.

FIGS. 5c and 6c illustrate call flow handover procedures during handoverexecution phase starting when the user equipment has indicated that ithas switched over to the target eNodeB using a“RRCConnectionReconfigurationComplete” message. Assuming that the targeteNodeB already has data forwarded from the source eNodeB and is ready tosend, one additional message “Send DL Data to UE” can be sent to PDCP tostart the data transmission to the user equipment. In someimplementations, the PDCP component in the iRRH can be pre-configuredusing a “L2 Config Request” message sent during the preparation phase,discussed above, to automatically start sending downlink data andaccepting uplink data as soon as the“RRCConnectionReconfigurationComplete” message with the appropriateC-RNTI identity is detected (as shown in FIG. 5d ).

To ensure that the data will be available at the target eNodeB before itneeds to be sent, the data forwarding procedure that takes place in thesource eNodeB can be optimized. FIGS. 5b and 6b illustrate exemplaryforwarding procedures for the S1-based (FIG. 5b ) and X2-based (FIG. 6b) handovers. If all PDCP functions are located in the iRRH, then therecan be three messages that traverse the fronthaul, which are gating thestart of the flowing of the forwarded data: “eNodeB Status TransferRequest,” “eNodeB Status Transfer Response” and “Start Data Forwarding”messages. Additionally, data must traverse the fronthaul from layer 2 ofthe source eNodeB to the centralized unit and then to the layer 2 of thetarget eNodeB. To optimize this call flow, some PDCP functions, such ascompression and SN numbering, can be optimized. Further, PDCP bufferscan be co-located in the iBBU along with layer 3 and GTP functions. Thisoptimization can eliminate sending of “Start Data Forwarding” messageall the way to PDCP, which can terminate locally. The “Status TransferRequest/Response” messages can be also terminated locally in the iBBU.

2. Handover Procedures in the User Plane on the Uplink

The uplink user-plane performance can be affected by the fronthaullatency, through which the traffic must traverse before being forwardedto the EPC over the backhaul link. If the iBBU is centralized at the COwith the S-GW and P-GW, then the S1 latency can be substantially zero.Thus, the increase in latency introduced by the fronthaul can be offsetby the reduction in latency from S1. The 3GPP Standards can also allowfor the buffered UL PDCP SDU received out of sequence in the sourceeNodeB to be forwarded to the target eNodeB. Even though the buffereddata to be forwarded does not gate the first few packets of data senttoward the EPC in the UL, it is important that the data forwarding iscarried out in a timely manner to avoid data flow from being interruptedwith subsequent packets.

In some implementations, to optimize handover procedures in the userplane on the uplink, some PDCP functions, e.g. compression and SNnumbering, and PDCP buffers can be co-located in the iBBU along with thelayer 3 and GTP functions. This can eliminate the need to forward the ULPDCP SDU all the way from the source iRRH to the target iRRH. Instead,the data can be forwarded from the PDCP buffers in the iBBU. In someexemplary implementations, impact on the uplink user-plane handoverperformance due to fronthaul latency can be similar to the one for thedownlink.

C. RRC Connection Establishment Procedure

FIGS. 7a-h illustrate details associated with an exemplary RRCconnection establishment procedure. In some implementations, thisprocedure can transition a user equipment from an idle state to anactive state and can include the following exchange ofcommands/messages: “RACH Access”, “RRC Connection EstablishmentRequest”, “S1 Setup”, “Initial Security Activation”, “UE CapabilityTransfer”, and “RRC Connection Reconfiguration” to start the downlinkdata flow from the EPC. In some implementations, the RACH Accessprocedure can be handled by layer 2 and thus might not involve anymessages traversing the fronthaul. In some implementations, where theiBBU's are centralized at the CO along with the EPC, the S1 interfacelatency can be assumed to be zero and thus can compensate for someincrease in latency due to the front haul.

FIG. 7a illustrates an exemplary RRC connection establishment procedure700, according to some implementations of the current subject matter.The procedure 700 can involve exchanging or traversing ofcommands/messages between PDCP component 711, RRC user equipment 713,RRM 715, S1 interface 717 and MAC layer 719.

As shown in FIG. 7a , the procedure 700 can be initiated by sending a“RRC-CONXN_REQ” message and completed by sending a“RRC_CONXN_SETUP_CMPLT” message from PDPC 711 to RRC user equipment 713.Between these two messages, five additional messages can traverse thefronthaul and thus, contribute to the procedure duration time. Thesemessages can include a pair of PDCP configurationmessages—“PDCP_ADDMOD_UE_PROFILE/RSP”; a pair of MAC configurationmessages—“DP_CONFIG_CREATE_UE_PROFILE/RSP”; and another RRCmessage—“RRC_CONXN_SETUP”. In some implementations, PDCP and MACmessages can be carried out in parallel and/or can be combined into asingle layer 2 Config/Rsp message.

In some implementations, to further reduce the procedure 700 duration,“RRC_CONXN_SETUP” can be combined with the “L2 Config” message, therebyfurther reducing number of messages traversing fronthaul by one. The “L2Config Rsp” message can also be combined with these two message, therebyfurther reducing number of messages and total duration time for theprocedure 700.

FIG. 7b illustrates an exemplary optimized RRC connection establishmentprocedure 710 in accordance with the optimization technique discussedabove. In particular, the combined messages can now be exchanged betweenRRC-UE 713, RRM 715, S1AP 725, and PDCP/RLC/MAC 727. As discussed abovein connection with FIG. 7a , the procedure begins with sending“RRC_CONXN_REQ” message and completes with sending“RRC_CONXN_SETUP_CMPLT” message from PDPC/RLC/MAC 727 to the RRC at theuser equipment 713. The “Dedicated RR Request” and “Dedicated RRResponse” messages are exchanged between RRC-UE 713 and RRM 715. Then,the combined message of “L2 Config Request” (which can include “RLC/MACCreate UE Profile” and “PDPC_ADDMOD UE Profile” messages) andRRC_CONXN_SETUP″ can be sent from RRC-UE 713 to PDCP/RLC/MAC 727. The“L2 Config Response” message can be sent back to the RRC-UE 713 andfollowed by the “RRC_CONXN_SETUP_CMPLT” message to complete the RRCconnection establishment procedure.

FIG. 7c illustrates an exemplary S1 interface setup procedure, accordingto some implementations of the current subject matter. The S1 setupprocedure can follow the RRC establishment procedure discussed inconnection with FIGS. 7a-b above. The S1 setup procedure can include apair of PDCP configuration messages traversing the fronthaul:“PDCP_ADDMOD_UE_PROFILE” and “PDCP_ADDMOD_UE_RSP” (between PDCP 711 andRRC-UE 713). FIG. 7d illustrates an exemplary initial securityactivation procedure that can follow the S1 interface setup procedure.This procedure can include an exchange of the following four messagesthat traverse the fronthaul: a pair of RRC messages (“RRC_SEC_MOD_CMD”and “RRC_SEC_MOD_COMPLETE” (between PDCP 711 and RRC-UE 713)) and a pairof PDCP configuration messages (“PDCP_ADDMOD_UE_PROFILE” and“PDCP_ADDMOD_UE_RSP” (between PDCP 711 and RRC-UE 713)). FIG. 7d alsoillustrates an exemplary UE capability transfer procedure. Thisprocedure can follow the initial security activation procedure discussedabove. It can include a pair of RRC messages(“RRC_UE_CAPABILITY_ENQUIRY” and “RRC_UE_CAPABILITY_INFO” (between PDCP711 and RRC-UE 713)). Thus, for these three procedures, there can beeight messages that can traverse the fronthaul.

In some implementations, the current subject matter system can optimizethese three procedures by combining some of the messages that areexchanged between its components into a single message. FIG. 7eillustrates an exemplary optimization technique that can reduce thenumber of messages traversing the fronthaul by a half by combining each“L2 Config” message with an RRC message.

As shown in FIG. 7e , the optimized procedure can begin with“S1C_NEW_ATTACH_REQ” AND “S1C_INITIAL_UE_CONTEX_SETUP” messagesexchanged between the RRC-UE 713 and S1AP 725. Then, a combination of“L2 Config Request” and “RRC_SEC_MOD_CMD” message can be sent fromRRC-UE 713 to the PDCP/RLC/MAC 727, where the “L2 Config Request” caninclude “PDCP_ADDMOD UE PROFILE” message. A “L2 Config Response” and“RRC_SEC_MOD_CMP” messages can follow from PDCP/RLC/MAC 727. The next L2Config message can be also a combination of “L2 Config Request” and“RRC_UE_CAPABILITY_ENQUIRY” messages that are sent from the RRC-UE 713to the PDCP/RLC/MAC 727, where the “L2 Config Request” can includePDCP_ADDMOD UE Profile” message. This combined message can be followedby “L2 Config Response” and “RRC_UE_CAPABILITY_INFO” message, therebycompleting the optimized procedure.

In some implementations, where the iBBU's are centralized at the COalong with the EPC, the overall delay impact of the fronthaul can beoffset by two S1-AP messages (“SIC_NEW_ATTACH_REQ” and“SIC_INITIAL_UE_CONTEXT_SETUP”), which can have a substantially zerotransport delay.

FIGS. 7f-g illustrate exemplary RRC connection reconfiguration and S1downlink activation procedures, according to some implementations of thecurrent subject matter. These procedures (i.e., exchange of messagesthat can traverse the fronthaul) can be performed after completion ofthe S1 setup, initial security activation and UE capability transferprocedures discussed above in connection with FIGS. 7c-e . The RRCconnection reconfiguration procedure (shown in FIG. 7c ) can be similarto the RRC connection establishment procedure (as shown in FIG. 7a ) andcan include a pair of PDCP (“PDCP_CONFIG_DEDICATED_REQ” and“PDCP_CONFIG_DEDICATED_RSP”) and a pair of MAC(“DP_CONFIG_DEDICATED_REQ” and “DP_CONFIG_DEDICATED_RSP”) configurationmessages followed by a pair of RRC messages between the eNodeB and theuser equipment. In some implementations, the PDCP and MAC configurationprocedures can occur in parallel and/or can be combined into a single L2Config/L2 Config Rsp procedure with two messages traversing thefronthaul. Further, similar to the RRC connection establishmentprocedure (shown in FIG. 7a ), the RRC connection reconfigurationprocedure can be optimized by combining the RRC messages with the L2Config messages, thereby, reducing the two pairs of messages to one.

In some implementations, once a data radio bearer (“DRB”) has beenestablished with the RRC connection reconfiguration procedure, theeNodeB can activate the downlink S1 bearer with the EPC to start a dataflow. However, the data flow might have to traverse the fronthaul andincur one segment delay before the user equipment state can beconsidered active.

FIG. 7h illustrates an exemplary optimized procedures for RRC connectionreconfiguration procedures, according to some implementations of thecurrent subject matter. As shown in FIG. 7h , the “L2 Config Request”can be combined with the “RRC_CONXN_RECONFIG_REQ” message, where the “L2Config Request” can include “RLC/MAC_CONFIG_DEDICATED_REQ” and“PDCP_ADDMOD UE Profile” messages, which can be sent to PCP/RLC/MAC 727from the RRC-UE 713. An “L2 Config Response” message followed by“RRC_CONXN_RECONFIG_COMPLETE” message can be received at the RRC-UE 713.At this point, RRC-UE 713 can send “S1AP_RRC_RB_STATUS_REPORT” messageto S1AP 725. Upon receipt of this message, the S1AP 725 can send a“DL_INFORMATION_TRANSFER” message to GTP Manager 733, which can containinformation on the downlink. The PDCP/RLC/MAC 727 can send the“UL_INFORMATION_TRANSFER” message to GTP Manager 733, which can containinformation on the uplink.

In some implementations, where the iBBU's can be centralized at the COalong with the EPC, the overall delay impact of the fronthaul can beoffset by one S1-AP message, “S1AP_RRC_RB_STATUS_REPORT”, and the startof the downlink data transfer from the EPC, both of which can have azero transport delay.

In some exemplary, non-limiting implementations, the RRC connectionestablishment procedure can be performed in a total of 10 messages beingtraversed across the fronthaul if the iBBU is co-located with the macrocell and just 6 messages if the iBBU is co-located with the centraloffice. As can be understood, the current subject matter system is notlimited to the above indicated values.

D. RRC Connection Re-Establishment Procedure

FIGS. 8a-d illustrate an exemplary RRC connection re-establishmentprocedure, according to some implementations of the current subjectmatter. The RRC connection re-establishment procedure can include twostages: an RRC connection re-establishment request stage and an RRCconnection re-configuration stage. Each stage's procedures can besimilar to the RRC connection establishment procedures shown in FIGS. 7a-g.

Similar to the RRC connection establishment procedure, the RRCconnection re-establishment procedure can be initiated by sending a“RRC_CONXN_REESTALISH_REQ” message and can be completed by sending“RRC_CONXN_REESTABLISH_CMPLT” message. As shown in FIGS. 8a-c (andsimilar to the RRC connection establishment procedure), the RRCconnection re-establishment procedure can include a pair of PDCPconfiguration messages (“PDCP_REESTABLISH_REQ” and“PDCP_REESTABLISH_RSP”) and a pair of MAC configuration messages(“MAC_REESTABISH_REQ” and “MAC_REESTABLISH_RSP”), which can be followedby a pair of RRC messages (“RRC_CONXN_RECONFIG_REQ” and“RRC_CONXN_REESTABLISH” and “RRC_CONXN_REESTABLISH_CMPLT”) between theeNodeB and the UE. The PDCP and MAC configuration procedures can occurin parallel and/or can be combined into a single L2 Config/L2 Config Rspprocedure, which can result in one pair of messages traversing thefronthaul.

FIG. 8d illustrates an exemplary optimized RRC connectionreestablishment procedure, according to some implementations of thecurrent subject matter. As shown in FIG. 8d , the“RRC_CONXN_REESTABLISH” message can be combined with an “L2 ConfigRequest” message, where the “L2 Config Request” message can include“MAC_REESTABLISH_REQ” and “PDPC_REESTABLISH_REQ” message, therebyreducing the two pairs of messages to one. This can be followed by an“L2 Config Response” message and “RRC_CONXN_REESTABLISH_CMPLT” message.Then, another combination of “L2 Config Request” message and“RRC_CONXN_RECONFIG_REQ” message can be sent, where the “L2 ConfigRequest” message can include “MAC_REESTABLISH_RESUME_REQUEST” and“PDPC_REESTABLISH_RESUME_REQUEST” message, thereby reducing the twopairs of messages to one. This can be followed by an “L2 ConfigResponse” message and “RRC_CONXN_RECONFIG_RSP” message.

In some exemplary, non-limiting implementations, the optimized procedurecan involve 5 messages for RRC connection re-establishment procedure asopposed to 9 messages in a non-optimized procedure. As can beunderstood, the current subject matter system is not limited to theabove indicated values.

In some implementations, the current subject matter can be configured tobe implemented in a system 900, as shown in FIG. 9. The system 900 caninclude one or more of a processor 910, a memory 920, a storage device930, and an input/output device 940. Each of the components 910, 920,930 and 940 can be interconnected using a system bus 950. The processor910 can be configured to process instructions for execution within thesystem 600. In some implementations, the processor 910 can be asingle-threaded processor. In alternate implementations, the processor910 can be a multi-threaded processor. The processor 910 can be furtherconfigured to process instructions stored in the memory 920 or on thestorage device 930, including receiving or sending information throughthe input/output device 940. The memory 920 can store information withinthe system 900. In some implementations, the memory 920 can be acomputer-readable medium. In alternate implementations, the memory 920can be a volatile memory unit. In yet some implementations, the memory920 can be a non-volatile memory unit. The storage device 930 can becapable of providing mass storage for the system 900. In someimplementations, the storage device 930 can be a computer-readablemedium. In alternate implementations, the storage device 930 can be afloppy disk device, a hard disk device, an optical disk device, a tapedevice, non-volatile solid state memory, or any other type of storagedevice. The input/output device 940 can be configured to provideinput/output operations for the system 900. In some implementations, theinput/output device 940 can include a keyboard and/or pointing device.In alternate implementations, the input/output device 940 can include adisplay unit for displaying graphical user interfaces.

FIG. 10 illustrates an exemplary method 1000 for coordinatingcommunication of data packets between a user device and a core network,according to some implementations of the current subject matter. In someimplementations, a first device (e.g., iBBU 304 as shown in FIG. 3) canbe communicatively coupled to the core network 108 (as shown in FIG. 3)and a second device (e.g., iRRH 302) can be communicatively coupled tothe first device. At 1002, data packets can be received from the userdevice by the second device. At 1004, the received data packets can betransmitted to the core network by the first device. In someimplementations, the first device and the second device can share atleast one functionality associated with layer 2 of a long term evolutionradio access network.

In some implementations, the current subject matter can also include oneor more of the following optional features. The first device can includeat least a portion of an evolved node (eNodeB) base station. The seconddevice can include a remote radio head. The remote radio head caninclude a radio transmitter and a radio receiver. In someimplementations, the functionality shared by the first and second devicecan be a packet data convergence protocol (“PDCP”).

In some implementations, the first device and the second device can becommunicatively coupled via a fronthaul Ethernet connection. The firstdevice can be communicatively coupled with the core network using abackhaul connection. At least one message in a plurality of messages cantraverse the fronthaul Ethernet connection. The messages can beassociated with establishing communication between the user device andthe core network. The plurality of messages can include messagesrelating to layer 1 and/or layer 2 configuration and messages relatingto establishing a radio resource control (“RRC”) connection. In someimplementations, the messages relating to layer 1 and/or layer 2configuration can be combined with messages relating to establishing theRRC connection, which can reduce latency associated with the Ethernetfronthaul connection. The messages can also include messages relating tore-establishing the RRC connection. Further, in some implementations,the messages relating to layer 1 and/or layer 2 configuration can becombined with the messages relating to re-establishing the remote radiocontrol RRC connection, which can also reduce latency associated withthe Ethernet fronthaul connection.

In some implementations, a third device can be communicatively coupledto the core network. The third device can include at least one of thefollowing: at least a portion of an evolved node (eNodeB) base stationand a remote radio head. The first device and the third device can be atleast one of the following: a macro cell and a micro cell. The firstdevice and the third device can exchange a plurality of messagesrelating to handover. The messages exchanged between the first deviceand the third device can also include messages relating to layer 1and/or layer 2 configuration. In some implementations, the messagesrelating to handover can be combined with messages relating to layer 1and/or layer 2 configuration. In some implementations, at least one ofthe second device and the third device, upon detecting a reconfigurationof a connection with the user device, can begin transmission of data ona downlink connection connecting the user device and at least one of thesecond device and the third device.

In some implementations, the current subject matter can relate to asystem (as well as a method and/or a computer program product) forcoordinating communication of data packets between a user device and acore network. The system can include a communications device that can becommunicatively coupled to the core network via a backhaul connection.The communications device can have at least one functionality associatedwith layer 2 of a long term evolution radio access network. In someimplementations, the communications device can include at least aportion of an evolved node (eNodeB) base station, where thefunctionality can relate to packet data convergence protocol (PDCP).

In some implementations, the current subject matter can relate to asystem (as well as a method and/or a computer program product) forcoordinating communication of data packets between a user device and acore network. The system can include a first communications device thatcan receive at least one data packet from the user device. The firstcommunications device can have at least one functionality associatedwith layer 2 of a long term evolution radio access network. In someimplementations, the first communications device can include a remoteradio head. The remote radio head can include a radio transmitter and aradio receiver. The functionality can relate to packet data convergenceprotocol (PDCP). Further, in some implementations, the firstcommunications device can be communicatively coupled to a second deviceusing a fronthaul Ethernet connection for exchanging at least onemessage relating to layer 1 and/or layer 2 configuration and/orestablishing a radio resource control (RRC) connection using PDCP.

In some implementations, the current subject matter can relate to acommunications device (as an associated method and computer programproduct), such as iBBU 304 shown in FIG. 3, that is a configured to becommunicatively coupled to a core network (e.g., core network 108 shownin FIG. 3) and a remote radio head (e.g., an iRRH 302 shown in FIG. 3)for coordinating communication of data packets between a user device(e.g., user equipment 104 shown in FIGS. 1a-c ) and the core network.The communications device can include a processing component (e.g.,component 320 as shown in FIG. 3) having at least one functionalityassociated with layer 2 of a long term evolution radio access network(e.g., PDCP-upper as shown and discussed in connection with FIG. 4). Thecommunications device and the remote radio head can be configured toshare that functionality.

In some implementations, the current subject matter can also include oneor more of the following optional features. The communications devicecan be a portion of an evolved node (eNodeB) base station. Thecommunications device and the remote radio head can be communicativelycoupled via a fronthaul Ethernet connection (e.g., fronthaul 306 shownin FIG. 3). The communications device can be communicatively coupledwith the core network using a backhaul connection (e.g., backhaul 308shown in FIG. 3).

In some implementations, at least one message in a plurality of messagescan traverse the fronthaul Ethernet connection. The plurality of messagecan be associated with establishing communication between the userdevice and the core network. The messages can include messages relatingto layer 1 and/or layer 2 configuration and messages relating toestablishing a RRC connection. Further, the messages relating to layer 1and/or layer 2 configuration can be combined with the messages relatingto establishing the RRC connection. This can reduce latency associatedwith the Ethernet fronthaul connection as discussed above in connectionwith FIGS. 3-8 d. In some implementations, the messages can includemessages relating to re-establishing the RRC connection. Additionally,the messages relating to layer 1 and/or layer 2 configuration can becombined with the messages relating to re-establishing the RRCconnection. This can further reduce latency associated with the Ethernetfronthaul connection, as discussed above in connection with FIGS. 3-8 d.

In some implementations, another communications device (e.g., an iRRHand/or an iBBU) can be communicatively coupled to the core network andcan communicate with the above communications device (e.g., iBBU 304).In some implementations, these devices can exchange a plurality ofmessages relating to handover. The messages can include messagesrelating to layer 1 and/or layer 2 configuration. Further, at least onemessage relating to handover can be combined with at least one messagerelating to layer 1 and/or layer 2 configuration. In someimplementations, the remote radio head (e.g., iRRH 302), upon detectinga reconfiguration of a connection with the user device, can transmitdata on a downlink connection connecting the user device and the remoteradio head.

In some implementations, the current subject matter relates to acommunications device (as well as an associated method and a computerprogram product) (e.g., iRRH 302) for coordinating communication of datapackets between a user device and a second communications device (e.g.,iBBU 304). The communications device can include a radio transmitter anda radio receiver (along power amplification component 312 and radiofrequency component 314). The communications device can also include aprocessing component (e.g., component 318 as shown in FIG. 3) having atleast one functionality associated with layer 2 of a long term evolutionradio access network, which can be shared with the second communicationsdevice (e.g., iBBU 304). In some implementations, the communicationsdevice can be coupled to the second communications device (e.g., iBBU304) using a fronthaul Ethernet connection. The communications devicecan be a remote radio head comprising a portion of an evolved node(eNodeB) base station. The communications device and the secondcommunications device (e.g, iBBU 304) can be communicatively coupled viaa fronthaul Ethernet connection and the second communications device(e.g, iBBU 304) is communicatively coupled with the core network using abackhaul connection. In some implementations, the communications device,upon detecting a reconfiguration of a connection with the user device,can transmit data on a downlink connection connecting the user deviceand the communications device.

The systems and methods disclosed herein can be embodied in variousforms including, for example, a data processor, such as a computer thatalso includes a database, digital electronic circuitry, firmware,software, or in combinations of them. Moreover, the above-noted featuresand other aspects and principles of the present disclosedimplementations can be implemented in various environments. Suchenvironments and related applications can be specially constructed forperforming the various processes and operations according to thedisclosed implementations or they can include a general-purpose computeror computing platform selectively activated or reconfigured by code toprovide the necessary functionality. The processes disclosed herein arenot inherently related to any particular computer, network,architecture, environment, or other apparatus, and can be implemented bya suitable combination of hardware, software, and/or firmware. Forexample, various general-purpose machines can be used with programswritten in accordance with teachings of the disclosed implementations,or it can be more convenient to construct a specialized apparatus orsystem to perform the required methods and techniques.

The systems and methods disclosed herein can be implemented as acomputer program product, i.e., a computer program tangibly embodied inan information carrier, e.g., in a machine readable storage device or ina propagated signal, for execution by, or to control the operation of,data processing apparatus, e.g., a programmable processor, a computer,or multiple computers. A computer program can be written in any form ofprogramming language, including compiled or interpreted languages, andit can be deployed in any form, including as a stand-alone program or asa module, component, subroutine, or other unit suitable for use in acomputing environment. A computer program can be deployed to be executedon one computer or on multiple computers at one site or distributedacross multiple sites and interconnected by a communication network.

As used herein, the term “user” can refer to any entity including aperson or a computer.

Although ordinal numbers such as first, second, and the like can, insome situations, relate to an order; as used in this document ordinalnumbers do not necessarily imply an order. For example, ordinal numberscan be merely used to distinguish one item from another. For example, todistinguish a first event from a second event, but need not imply anychronological ordering or a fixed reference system (such that a firstevent in one paragraph of the description can be different from a firstevent in another paragraph of the description).

The foregoing description is intended to illustrate but not to limit thescope of the invention, which is defined by the scope of the appendedclaims. Other implementations are within the scope of the followingclaims.

These computer programs, which can also be referred to programs,software, software applications, applications, components, or code,include machine instructions for a programmable processor, and can beimplemented in a high-level procedural and/or object-orientedprogramming language, and/or in assembly/machine language. As usedherein, the term “machine-readable medium” refers to any computerprogram product, apparatus and/or device, such as for example magneticdiscs, optical disks, memory, and Programmable Logic Devices (PLDs),used to provide machine instructions and/or data to a programmableprocessor, including a machine-readable medium that receives machineinstructions as a machine-readable signal. The term “machine-readablesignal” refers to any signal used to provide machine instructions and/ordata to a programmable processor. The machine-readable medium can storesuch machine instructions non-transitorily, such as for example as woulda non-transient solid state memory or a magnetic hard drive or anyequivalent storage medium. The machine-readable medium can alternativelyor additionally store such machine instructions in a transient manner,such as for example as would a processor cache or other random accessmemory associated with one or more physical processor cores.

To provide for interaction with a user, the subject matter describedherein can be implemented on a computer having a display device, such asfor example a cathode ray tube (CRT) or a liquid crystal display (LCD)monitor for displaying information to the user and a keyboard and apointing device, such as for example a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well. For example,feedback provided to the user can be any form of sensory feedback, suchas for example visual feedback, auditory feedback, or tactile feedback;and input from the user can be received in any form, including, but notlimited to, acoustic, speech, or tactile input.

The subject matter described herein can be implemented in a computingsystem that includes a back-end component, such as for example one ormore data servers, or that includes a middleware component, such as forexample one or more application servers, or that includes a front-endcomponent, such as for example one or more client computers having agraphical user interface or a Web browser through which a user caninteract with an implementation of the subject matter described herein,or any combination of such back-end, middleware, or front-endcomponents. The components of the system can be interconnected by anyform or medium of digital data communication, such as for example acommunication network. Examples of communication networks include, butare not limited to, a local area network (“LAN”), a wide area network(“WAN”), and the Internet.

The computing system can include clients and servers. A client andserver are generally, but not exclusively, remote from each other andtypically interact through a communication network. The relationship ofclient and server arises by virtue of computer programs running on therespective computers and having a client-server relationship to eachother.

The implementations set forth in the foregoing description do notrepresent all implementations consistent with the subject matterdescribed herein. Instead, they are merely some examples consistent withaspects related to the described subject matter. Although a fewvariations have been described in detail above, other modifications oradditions are possible. In particular, further features and/orvariations can be provided in addition to those set forth herein. Forexample, the implementations described above can be directed to variouscombinations and sub-combinations of the disclosed features and/orcombinations and sub-combinations of several further features disclosedabove. In addition, the logic flows depicted in the accompanying figuresand/or described herein do not necessarily require the particular ordershown, or sequential order, to achieve desirable results. Otherimplementations can be within the scope of the following claims.

What is claimed:
 1. A computer-implemented method for coordinatingcommunication of a plurality of data packets, wherein a first radiodevice and a second radio device in a plurality of radio devices arecommunicatively coupled to a baseband unit device in a plurality ofbaseband unit devices, the method comprising: receiving, using thesecond radio device, data packets from at least one user device;transmitting, using the second radio device, the data packets to thefirst radio device; generating, using at least one of the first radiodevice and the second radio device, a buffer occupancy report;transmitting, at least one of the first radio device and the secondradio device, the generated buffer occupancy report to the baseband unitdevice; and controlling transmission, by the baseband unit device, basedon the generated buffer occupancy report, of one or more data packetsbetween the baseband unit device and at least one of the first radiodevice and the second radio device; wherein the first radio device andthe second radio device share at least one functionality associated withlayer 2 of a long term evolution radio access network, the at least onefunctionality including a packet data convergence protocol (PDCP)functionality, the PDCP functionality is split between the first radiodevice, the second radio device, and the baseband unit device; whereinthe baseband unit device includes a first PDCP portion of the at leastone functionality, the first radio device includes a second PDCP portionand the second radio device includes a third PDCP portion of the atleast one functionality, the first PDCP portion coordinates transmissionof at least one compressed and sequence-numbered data packet from thebaseband unit device to at least one scheduler of the first and secondradio devices based on a buffer occupancy report generated by the thirdPDCP portion in the second radio device and transmitted to the firstradio device.
 2. The method according to claim 1, wherein the basebandunit device comprises at least a portion of an evolved node (eNodeB)base station; the first radio device and the second radio device includeat least one a remote radio head, the remote radio head including aradio transmitter and a radio receiver, the baseband unit device iscommunicatively coupled with a core network using a backhaul connection;the first radio device and the second radio device are communicativelycoupled with the baseband unit device using at least one fronthaulEthernet connection, wherein a plurality messages being associated withestablishing communication between the at least one user device and thecore network.
 3. The method according to claim 1, wherein the firstradio device is a primary cell remote radio head communicatively coupledwith the baseband unit; the second radio device is a secondary cellremote radio head communicatively coupled to the first radio device. 4.The method according to claim 1, further comprising executing a handoverprocedure from the first radio device to another first radio device inthe plurality of first radio devices; communicating with the anotherfirst radio device; and transmitting at least one data packet using theanother first radio device.
 5. The method according to claim 1, furthercomprising determining location of the at least one user device;selecting another second radio device from the plurality of second radiodevices based on the determined location of the at least one userdevice; and transmitting at least one data packet using the selectedanother second radio device.
 6. The method according to claim 1, whereinthe transmitted at least one data packet is a compressed and sequencenumbered data packet.
 7. The method according to claim 1, furthercomprising removing, by at least one of the first radio device and thesecond radio device, at least one data packet from a buffer of at leastone of the first radio device and the second radio device based on adetermination that the at least one data packet has expired.
 8. Themethod according to claim 1, further comprising allocating, by the firstradio device, at least one radio link control (RLC) packet data unit(PDU) sequence number to the second radio device; and determining, basedon the allocated at least one RLC PDU sequence number, at least oneunacknowledged packet data unit transmitted to the user equipment by thesecond radio device.
 9. The method according to claim 1, furthercomprising determining, by the second radio device, at least one userdevice that will transmit at least one data packet prior to transmissionof the at least one data packet; determining, by the second radiodevice, at least one physical uplink control channel (PUCCH) resourcefor use of a receipt of an acknowledgement/non-acknowledgement for atransmission of the at least one data packet by the second radio deviceto the at least one user device; and providing, by the second radiodevice, the at least one determined PUCCH resource to the first radiodevice.
 10. A system for coordinating communication of a plurality ofdata packets, wherein a first radio device and a second radio device ina plurality of radio devices are communicatively coupled to a basebandunit device in a plurality of baseband unit devices, the systemcomprising: at least one memory; and at least one processor operativelycoupled to the memory, the at least one processor being configured to:receiving, using the second radio device, data packets from at least oneuser device; transmitting, using the second radio device, the datapackets to the first radio device; generating, using at least one of thefirst radio device and the second radio device, a buffer occupancyreport; transmitting, at least one of the first radio device and thesecond radio device, the generated buffer occupancy report to thebaseband unit device; and controlling transmission, by the baseband unitdevice, based on the generated buffer occupancy report, of one or moredata packets between the baseband unit device and at least one of thefirst radio device and the second radio device; wherein the first radiodevice and the second radio device share at least one functionalityassociated with layer 2 of a long term evolution radio access network,the at least one functionality including a packet data convergenceprotocol (PDCP) functionality, the PDCP functionality is split betweenthe first radio device, the second radio device, and the baseband unitdevice; wherein the baseband unit device includes a first PDCP portionof the at least one functionality, the first radio device includes asecond PDCP portion and the second radio device includes a third PDCPportion of the at least one functionality, the first PDCP portioncoordinates transmission of at least one compressed andsequence-numbered data packet from the baseband unit device to at leastone scheduler of the first and second radio devices based on a bufferoccupancy report generated by the third PDCP portion in the second radiodevice and transmitted to the first radio device.
 11. The systemaccording to claim 10, wherein the baseband unit device comprises atleast a portion of an evolved node (eNodeB) base station; the firstradio device and the second radio device include at least one a remoteradio head, the remote radio head including a radio transmitter and aradio receiver, the baseband unit device is communicatively coupled witha core network using a backhaul connection; the first radio device andthe second radio device are communicatively coupled with the basebandunit device using at least one fronthaul Ethernet connection, wherein aplurality messages being associated with establishing communicationbetween the at least one user device and the core network.
 12. Thesystem according to claim 10, wherein the first radio device is aprimary cell remote radio head communicatively coupled with the basebandunit; the second radio device is a secondary cell remote radio headcommunicatively coupled to the first radio device.
 13. The systemaccording to claim 10, wherein the operations further comprise executinga handover procedure from the first radio device to another first radiodevice in the plurality of first radio devices; communicating with theanother first radio device; and transmitting at least one data packetusing the another first radio device.
 14. The system according to claim10, wherein the operations further comprise determining location of theat least one user device; selecting another second radio device from theplurality of second radio devices based on the determined location ofthe at least one user device; and transmitting at least one data packetusing the selected another second radio device.
 15. The system accordingto claim 10, wherein the transmitted at least one data packet is acompressed and sequence numbered data packet.
 16. The system accordingto claim 10, wherein the operations further comprise removing, by atleast one of the first radio device and the second radio device, atleast one data packet from a buffer of at least one of the first radiodevice and the second radio device based on a determination that the atleast one data packet has expired.
 17. The system according to claim 10,wherein the operations further comprise allocating, by the first radiodevice, at least one radio link control (RLC) packet data unit (PDU)sequence number to the second radio device; and determining, based onthe allocated at least one RLC PDU sequence number, at least oneunacknowledged packet data unit transmitted to the user equipment by thesecond radio device.
 18. The system according to claim 10, wherein theoperations further comprise determining, by the second radio device, atleast one user device that will transmit at least one data packet priorto transmission of the at least one data packet; determining, by thesecond radio device, at least one physical uplink control channel(PUCCH) resource for use of a receipt of anacknowledgement/non-acknowledgement for a transmission of the at leastone data packet by the second radio device to the at least one userdevice; and providing, by the second radio device, the at least onedetermined PUCCH resource to the first radio device.
 19. A computerprogram product for coordinating communication of a plurality of datapackets, wherein a first radio device and a second radio device in aplurality of radio devices are communicatively coupled to a basebandunit device in a plurality of baseband unit devices, comprising anon-transitory machine-readable medium storing instructions that, whenexecuted by at least one programmable processor, cause the at least oneprogrammable processor to perform operations comprising: receiving,using the second radio device, data packets from at least one userdevice; transmitting, using the second radio device, the data packets tothe first radio device; generating, using at least one of the firstradio device and the second radio device, a buffer occupancy report;transmitting, at least one of the first radio device and the secondradio device, the generated buffer occupancy report to the baseband unitdevice; and controlling transmission, by the baseband unit device, basedon the generated buffer occupancy report, of one or more data packetsbetween the baseband unit device and at least one of the first radiodevice and the second radio device; wherein the first radio device andthe second radio device share at least one functionality associated withlayer 2 of a long term evolution radio access network, the at least onefunctionality including a packet data convergence protocol (PDCP)functionality, the PDCP functionality is split between the first radiodevice, the second radio device, and the baseband unit device; whereinthe baseband unit device includes a first PDCP portion of the at leastone functionality, the first radio device includes a second PDCP portionand the second radio device includes a third PDCP portion of the atleast one functionality, the first PDCP portion coordinates transmissionof at least one compressed and sequence-numbered data packet from thebaseband unit device to at least one scheduler of the first and secondradio devices based on a buffer occupancy report generated by the thirdPDCP portion in the second radio device and transmitted to the firstradio device.